Thursday, April 20, 2017

Number of 1 Bits

Number of 1 Bits
Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as the Hamming weight).
For example, the 32-bit integer ’11' has binary representation 00000000000000000000000000001011, so the function should return 3.
Thoughts:
Using bit manipulation. Every time right shift 1 bit to get the bit is 1 or not. 
Note:  n >>> s is n right-shifted s bit positions with zero-extension.
Java Solution:
public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int result = 0;
        while(n != 0){
            result += n & 1; 
            n >>>= 1; 
        }
        return result;
    }
}

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